In areas with a high prevalence of tuberculosis, adenosine deaminase (ADA) is used as a rapid diagnostic test for tuberculous peritonitis1 and can also distinguish tuberculosis from other causes of ascites2, 3.

ADA levels in ascitic fluid, in conjunction with mycobacterial culture and response to anti-tuberculosis therapy, can direct initiation of medication treatment for tuberculosis1.

ADA is a marker of immune response. Due to immunosuppression associated with advanced liver disease, or a dilutional occurrence associated with malnutrition, ADA in peritoneal fluid is limited when used as a diagnostic aid1.

HIV status does not appear to affect ADA levels in tuberculous peritonitis1.

Efficacy

Where tuberculosis (TB) is prevalent, at a cut-off level of 30 to 40 units/L, adenosine deaminase (ADA) measurement in peritoneal fluid had an efficiency rating of 90% for diagnosing tuberculous peritonitis in patients with ascites1.

In a prospective study of 64 patients with ascites, 11 of which tested positive for TB, mean ADA level in the peritoneal fluid of the TB patients was 112.6 units/L compared with 16.3 units/L in the other patients, confirming tuberculous peritonitis in the TB patients2.

In a prospective study of 66 patients with ascites, 10 patients with tuberculous peritonitis had median ADA values of 108.5 units/L (range from 72.5 to 148 units/L). In patients with serous effusions, sensitivity and specificity values were high for the ADA test when used to diagnose early tuberculosis3.

Because of a lower prevalence of TB in North America, testing ascites fluid for ADA has a lower positive predictive value2.

Accuracy

Sensitivity

A retrospective study of 82 patients, 41 with confirmed tuberculous peritonitis and 41 controls, had a 95% sensitivity for using adenosine deaminase (ADA) in ascitic fluid to confirm tuberculous peritonitis2.

In a prospective study of 64 patients with ascites, ADA measured in peritoneal fluid to confirm tuberculous peritonitis in 11 patients had a sensitivity of 100%2.

Specificity

A retrospective study of 82 patients, 41 with confirmed tuberculous peritonitis and 41 controls, had a 98% specificity for using ADA in ascitic fluid to confirm tuberculous peritonitis2.

In a prospective study of 64 patients with ascites, ADA measured in peritoneal fluid to confirm tuberculous peritonitis in 11 patients had a specificity of 96%2.

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